U.S. patent application number 12/493077 was filed with the patent office on 2010-01-07 for induction heating system with versatile inductive cartridge.
Invention is credited to Bogdan Popescu.
Application Number | 20100000980 12/493077 |
Document ID | / |
Family ID | 41463546 |
Filed Date | 2010-01-07 |
United States Patent
Application |
20100000980 |
Kind Code |
A1 |
Popescu; Bogdan |
January 7, 2010 |
Induction Heating System with Versatile Inductive Cartridge
Abstract
Disclosed are devices and systems for inductive heating of a
liquid or food, which comprise versatile inductive heating
cartridges. To be able to use a normally inductively non-heatable
cup or vessel made of a generally dielectric material with an
induction heating unit, a removable cartridge made of an
inductively heatable material is inserted into the vessel. In one
embodiment, the cartridge is retained in the vessel by an
attachment functionality which prevents the cartridge from sliding
or flipping when the cup or vessel is tipped to serve or pour. The
attachment functionality is disengageable, and the cartridge may be
transferred from cup to cup or vessel to vessel by the user. In
another embodiment, the cartridges are configured to more
efficiently work with the "pot detection" circuits of modern
inductive hot plates or ranges. In another embodiment, the
cartridge includes an RFID tag, antenna, and sensor package.
Inventors: |
Popescu; Bogdan; (Redmond,
WA) |
Correspondence
Address: |
Bodgan Popescu
6228 159th Place NE
Redmond
WA
98052
US
|
Family ID: |
41463546 |
Appl. No.: |
12/493077 |
Filed: |
June 26, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61133809 |
Jul 2, 2008 |
|
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|
Current U.S.
Class: |
219/201 ;
219/438 |
Current CPC
Class: |
A47J 36/32 20130101;
A47J 36/2411 20130101; A47J 36/2444 20130101; H05B 6/1209 20130101;
A47J 36/2433 20130101; Y02B 40/00 20130101; Y02B 40/123 20130101;
A47J 36/2466 20130101; A47J 36/20 20130101; H05B 2213/06
20130101 |
Class at
Publication: |
219/201 ;
219/438 |
International
Class: |
H05B 6/02 20060101
H05B006/02; H05B 6/12 20060101 H05B006/12 |
Claims
1. A reusably insertable heating cartridge for inductively heating
a food or a liquid in an inside cavity of a cup or vessel, said cup
or vessel having a base and walls, said base composed substantially
of a dielectric material, which comprises: a) a cartridge body for
insertion into said inside cavity of said cup or vessel, said
cartridge body having upper face, peripheral edge and undersurface,
and further comprising a sheet or layer of an inductively heatable
material, said sheet or layer having dimensions, volume
distribution, and material properties configured to dissipate power
as heat when operatively coupled to an external oscillating
magnetic field penetrating said base or walls and contacting said
cartridge body; b) further comprising a latching functionality for
securing said cartridge body within said cavity of said cup or
vessel, wherein said latching functionality is disengageable by the
user for transferring said cartridge from cup to cup or vessel to
vessel; and c) wherein optionally said cartridge body comprises an
exterior sanitary coating of a food- or liquid-compatible
material.
2. The insertable heating cartridge of claim 1, wherein said
latching functionality is a mechanical latch configured to secure
said cartridge within said inside cavity of said cup or vessel.
3. The insertable heating cartridge of claim 2, wherein said
mechanical latch comprises at least one elastic projection from
said peripheral edge of said cartridge body, wherein said elastic
projection is configured for grippingly securing said cartridge
body between opposing walls of said cup or vessel.
4. The insertable heating cartridge of claim 2, wherein said
mechanical latch comprises a clippable appendage projecting from
said peripheral edge of said cartridge body, wherein said clippable
appendage is configured for grippingly securing said cartridge to a
lip of said walls of said cup or vessel.
5. The insertable heating cartridge of claim 2, wherein said
mechanical latch comprises a friction collar applied to a centrally
disposed hole in said cartridge body and adapted for securing said
cartridge to a post projecting centrally from said base of said cup
or vessel, or a friction collar applied to said peripheral edge of
said cartridge body and adapted for securing said cartridge
peripherally to said walls of said cup or vessel.
6. The insertable heating cartridge of claim 2, wherein said
mechanical latch comprises latching arms attached to a bezel around
a centrally disposed hole in said cartridge body, said latching
arms having barbs for mating with a barb-receiving post projecting
centrally from said base of said cup or vessel, or latching arms
attached to said peripheral edge of said cartridge body for mating
with barb receiving receptacles in said walls of said cup or
vessel.
7. The insertable heating cartridge of claim 2, wherein said
mechanical latch comprises at least two contralaterally placed pins
or slots on said peripheral edge of said cartridge body, wherein
said pins or slots are configured for engaging mating threadable
channels or bosses in said vessel.
8. The insertable heating cartridge of claim 1, wherein said
latching functionality is a magnetic latch, said magnetic latch
comprising a combination of a magnet applied externally on the base
or walls of said cup or vessel or encapsulated within said base or
walls and a magnetically responsive element in said cartridge body,
said magnet for magnetically attracting said magnetically
responsive element and thereby magnetically secured said cartridge
body within said inside cavity of said cup or vessel.
9. The insertable heating cartridge of claim 1, wherein said sheet
or layer of inductively heatable material is composed of iron, cast
iron, steel, carbon steel, stainless steel, martensitic stainless
steel, cobalt steel, chrome steel, nickel steel, silicon steel,
magnetic stainless steel, spring steel, mu-metal, aluminum, copper
or an alloy or a combination thereof.
10. The insertable heating cartridge of claim 1, wherein said
cartridge body further embodies a safety feature selected from the
group consisting of: a) encapsulated in said cartridge body, an
RFID tag and antenna configured to respond to a communication
protocol for verifying compatibility of said cartridge and an
inductive heating unit; b) encapsulated in said cartridge body, an
RFID tag and antenna, said cartridge body further comprising a
temperature sensor circuit in communication with said RFID tag for
transmitting a temperature datum to a microcontroller of an
inductive heating unit; c) within said cartridge body, a buoyant
cavity, wherein said buoyant cavity is configured for buoying said
cartridge in a liquid when said cartridge is not latchedly secured
in said cavity of said cup or vessel; and d) for forming said sheet
or layer of an inductively heatable material, a inductively
heatable material selected for a Curie temperature of less than
600.degree. F., more preferably less than 500.degree. F., and most
preferredly about 300.degree. F.
11. A combination for inductively heating a food or a liquid, which
comprises a) an insertable heating cartridge of claim 1; b) a cup
or vessel of said combination, said cup or vessel having walls, lip
and a base, wherein said cup or vessel is configured for receiving
and reversibly securing said insertable heating cartridge within
said inside cavity by a mechanical latching functionality or a
magnetic latching functionality, and wherein said latching
functionality is disengageable by the user for transferring said
insertable heating cartridge from cup to cup or vessel to
vessel.
12. An inductive heating unit, wherein said inductive heating unit
is configured to operate with said heating cartridge of claim
1.
13. A reusably insertable heating cartridge for inductively heating
a food or a liquid in an inside cavity of a cup or vessel, said cup
or vessel having a base and walls, said base composed substantially
of a dielectric material, which comprises: a) a cartridge body for
insertion into said inside cavity of said cup or vessel, said
cartridge body having upper face, peripheral edge, and
undersurface, and further comprising a sheet or layer of an
inductively heatable material, said sheet or layer having
dimensions, volume distribution, and material properties configured
to dissipate power as heat when operatively coupled to an external
oscillating magnetic field penetrating said base or walls and
contacting said cartridge body; and b) encapsulated in said
cartridge body, i) an RFID chip and antenna; ii) optionally a
temperature sensor in electronic communication with said RFID tag
and antenna; and c) optionally wherein said cartridge body
comprises an exterior sanitary coating of a food- or
liquid-compatible material.
14. The insertable heating cartridge of claim 13, wherein said
sheet or layer of inductively heatable material is composed of
iron, cast iron, steel, carbon steel, stainless steel, martensitic
stainless steel, cobalt steel, chrome steel, nickel steel, silicon
steel, magnetic stainless steel, spring steel, mu-metal, aluminum,
copper or an alloy or a combination thereof.
15. A combination for inductively heating a food or a liquid, which
comprises a) an insertable heating cartridge of claim 13; b) a cup
or vessel of said combination, wherein said cup or vessel is
configured for removably receiving said insertable heating
cartridge.
16. An inductive heating unit, wherein said inductive heating unit
is configured to operate with said insertable heating cartridge of
claim 13.
17. A reusably insertable heating cartridge for inductively heating
a food or a liquid in an inside cavity of a cup or vessel, said cup
or vessel having a base and walls, said base composed substantially
of a dielectric material, which comprises: a) a cartridge body for
insertion into said inside cavity of said cup or vessel, said
cartridge body having upper face, peripheral edge and undersurface,
b) wherein said cartridge body comprises a sheet of an inductively
heatable material; and wherein said sheet is further characterized
as having an array of perforations or dimples configured to
increase apparent inductive load resistance of said heating
cartridge due to eddy current losses when operatively coupled to an
external oscillating magnetic field penetrating said base or walls
and contacting said cartridge body.
18. The insertable heating cartridge of claim 17, wherein said
sheet of inductively heatable material is composed of iron, cast
iron, steel, carbon steel, stainless steel, martensitic stainless
steel, cobalt steel, chrome steel, nickel steel, silicon steel,
magnetic stainless steel, spring steel, mu-metal, aluminum, copper,
an inductively heatable material selected for a Curie temperature
of less than 600.degree. F., or an alloy or a combination
thereof.
19. A combination for inductively heating a food or a liquid, which
comprises a) an insertable heating cartridge of claim 17; b) a cup
or vessel of said combination, wherein said cup or vessel is
configured for removably receiving said insertable heating
cartridge.
20. An inductive heating unit, wherein said inductive heating unit
is configured to operate with said insertable heating cartridge of
claim 17.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to U.S. Provisional Patent
Application Ser. No. 61/133,809, filed 2008 Jul. 2, from which
priority is claimed, and which is herein incorporated in full by
reference.
TECHNICAL FIELD
[0002] This invention is related to devices for inductive heating
of foods or liquids and vessels and appliances for use
therewith.
BACKGROUND
[0003] A long tradition of electrical heating of a food or liquid
in a cup or vessel relies on the use of resistive electrical
heating elements directly or indirectly contacted with the vessel.
As representative of the art, heat is either transferred through
the base or walls of the vessel or generated in the vessel's
baseplate. Basal heating can be seen for example, in U.S. Pat. Nos.
3,778,594 to Wightman, 4,523,083 to Hamilton, and 4,980,539 to
Walton. Modifications of the base of the vessel to improve heat
transfer are disclosed in U.S. Pat. Nos. 6,192,787 to Montalto and
7,022,946 to Sanoner. Lateral wall heating is seen in U.S. Pat.
Nos. 6,082,114 to Leonoff and 6,870,135 to Hamm, for example. Thus
the familiar elements of the art involve conventional heat transfer
by heating the base or side wall of the vessel. Similar devices
have been provided for other vessels, for example baby bottles, as
described in U.S. Pat. No. 2,640,907 and US Pat. Appl No.
2008/0087659, and references cited therein.
[0004] Magnetic induction heating is both faster and more
energy-efficient than traditional resistive or gas stove units, and
is a "green" technology. According to industry figures, induction
heating efficiency is about 90%, as compared to 40% for gas burners
and 47% for electric ranges. Advantageously, the stovetop or "hob"
is not heated, reducing the risk of burn injury and fire. Unwanted
radiative and convective heating of the surrounding workspace is
also reduced. However, the range of vessels that can be used with
these systems is somewhat limited. Electrically conductive
materials like ferromagnetic metals and aluminum or copper can all
be used, but their requirements are quite different and usually
induction heating units are designed to work with either one or the
other or the prices are driven significantly up. It has been
largely accepted that ceramic, glass, or plastic vessels cannot be
used with induction heating systems.
[0005] Specially fabricated vessels are also used for this
technology, the base of the vessels may comprise several metal
layers, at least one of which evolves heat when exposed to an
oscillating magnetic field.
[0006] Ferromagnetic materials, for example, respond to oscillating
magnetic fields by heating. The magnetic field generated by a coil
generates eddy currents and magnetic hysteresis in the
ferromagnetic material, leading to heating in direct relation to
the electrical power expended. This well known phenomenon has been
used for inductive ovens, hotplates, and the like.
[0007] The new inductive heating technologies have been applied in
a manner analogous to the older art of resistive heating. The wall
of the vessel is somehow heated and the heat finds its way to the
food or beverage inside the vessel. This can be seen for example in
U.S. Pat. No. 4,110,588 to Holz, where inductive energy is used to
heat a metal base of a cup. As recognized by Kim, in U.S. Pat. No.
6,936,799, the question as to what material the base of the cooking
container is made of must be first answered in order to determine
the nature and power of the inductive pulses applied thereto. Kim
devises a circuit for differentiating ferromagnetic and dielectric
vessels, but offers no solution as to how to apply inductive
heating to dielectric and non-ferromagnetic vessels.
[0008] Other pot detection circuitry is described by Moreland (U.S.
Pat. No. 3,796,850). Moreland observes that the hob may be provided
with a permanent magnet positioned under a dielectric ceramic glass
surface in order to detect the presence of a suitable vessel for
inductive cooking before applying power as a matter of safety.
[0009] Descriptions of inductive appliances for cooking include,
while not cumulatively, Ogino (U.S. Pat. No. 4,595,814), Aoki (U.S.
Pat. No. 4,638,135), Panecki (U.S. Pat. No. 4,908,489, Boys (U.S.
Pat. No. 5,450,305); and Clothier (U.S. Pat. No. 6,953,919), the
latter including an extensive review of the literature surrounding
inductive cooking and making provision for control via an RFID
"class of object" tag in the handle of a specially formed vessel.
Again, no provision is made for heating the contents of vessels
made without an inductively heatable baseplate.
[0010] Modification of the base of the vessel has been considered.
As described for example in U.S. Pat. No. 6,635,855 to Scaburri, in
order to more intimately associate a ferromagnetic material with
the baseplate of a non-ferrous vessel, the vessel is diecast with
embedded wire gauze in the base. This is an improvement over the
prior art, where the ferromagnetic gauze was simply applied
underneath the non-ferrous baseplate so that the base of the vessel
is heated from outside. Although this method ensures that the wire
gauze does not dissociate from the vessel, perhaps not
surprisingly, both such methods were reported to result in warping
or breakage of the base.
[0011] Harnden, in U.S. Pat. No. 3,745,290, addresses the use of
metal sheeting applied within an outer shell that is not
inductively heatable. The outer shell, with baseplate, is modified
with an inner lining by application of a vapor deposited metallic
coating, foil or sheet composite, embedded powdered metal or
embedded wires. In expired U.S. Pat. No. 3,786,222, disposable
aluminum foil is wrapped directly around the food or inserted in a
container, however, inductive heating with aluminum is not
generally accepted in the market because of the need for
specialized resonant circuitry, again defeating the object of a
inductive heating element for exchangeable use with containers that
are not inductively heatable.
SUMMARY
[0012] In extending the breadth of applications for inductive
heating to new consumer markets, no prior consideration has been
given to the advantages of reversibly inserting a ferromagnetic
material inside a non-inductively responsive vessel, where the
ferromagnetic material is packaged as a reusable, immersible member
that can be transferred from cup to cup or vessel to vessel as
desired by the user. Such a cartridge may be used with any vessel
that does not shield the cartridge from the magnetic field of an
external inductive heating unit. Food or liquid in vessels made of
ceramic, glass or plastic, which are not inductively heatable, may
be heated with the insertable cartridge of the invention.
[0013] In the devices and applications disclosed herein, an
induction "cartridge" or "puck" made of an inductively heatable
member, for example a sheet or layer of a ferromagnetic material
configured as a disk or plate, is inserted into and rests in
proximity to the bottom or a lower aspect of the inside cavity of a
vessel, where it can be heated by the primary coil of an inductive
heating unit on which the vessel is placed. Different coil
geometries can be chosen to best work with a specific induction
cartridge configuration by following the contour and the likely
paths of the induced eddy currents. The cartridge layer is also
selected with dimensions, volume distributions, thicknesses, and
magnetic permittivity suitable for optimal dissipation of power as
heat.
[0014] Applicable vessels include cups, bowls, coffee mugs, mugs
for a car, crock pots, kettles, baby bottles, and the like, of
off-the-shelf designs and sizes, or more generally, any portable
vessels made of dielectric materials like ceramic, glass, or
plastics suitable for use with food or drink. The vessel has at
least a base composed substantially of or composed essentially of a
dielectric material, which will not shield the inside cavity of the
vessel from the penetration of the external oscillating magnetic
field of the primary coil.
[0015] In order to allow for drinking or sipping the liquid from
the vessel without removing the induction cartridge, which
otherwise could slide or flip when the vessel is tilted for
gravitational drinking, retaining means are provided. The induction
cartridge is reusable and is easily removable for cleaning. For an
induction cartridge design to be used with baby bottles, a buoyant
float in the cartridge will cause the cartridge to float in the
bottle when inverted so that it does not obstruct the flow of the
liquid to the nipple.
[0016] In another aspect, the cartridge includes an RFID (Radio
Frequency Identification) tag that can be detected and recognized
by an induction heating unit. The coil used for induction heating
can be used for generating and receiving the RFID signals or a
secondary coil and antenna at generally a higher frequency can be
used. A suitable frequency and separation distance, typically a few
centimeters, for reliable transmission of data is chosen. Induction
heating units may be designed to power down unless a compatible
cartridge with RFID tag is detected, a feature that serves to
enhance safety if desired. Advantageously, the transmission from
the RFID tag can also selectively activate and deactivate the
induction coil to maintain a prescribed temperature when used with
an embedded temperature sensor in the cartridge. By potting the tag
and associated circuitry in a moisture resistant matrix, moisture
sensitivity is overcome. Unlike the prior art, the RFID chip on the
inventive cartridge may be moved from cup to cup or pot to pot. In
prior art pots for induction cooking, the RFID chip is placed in
the handle of the pot because the antenna would be RF shielded and
ineffective if placed inside the cooking cavity of a conductive
pot.
[0017] In one embodiment of the invention, the induction cartridge
assembly with RFID chip may have a "latching functionality" for
securing the cartridge in the vessel; in another embodiment, the
cartridge with RFID chip is not provided with any latching
functionality, depending on the specific application and the needs
of the user. When present, the latching function may be reversibly
disengaged, so that for either embodiment the cartridge may be
transferred from cup to cup or vessel to vessel by the user without
loss of utility.
[0018] Thus in a first embodiment, the invention is a reusably
insertable heating cartridge for inductively heating a food or a
liquid in an inside cavity of a cup or vessel, the cup or vessel
having a base and walls, where the base is composed substantially
of a dielectric material, which comprises: a) a cartridge body for
insertion into the inside cavity of the cup or vessel, the
cartridge body having upper face, peripheral edge and undersurface,
and further comprising a layer, sheet or plate of an inductively
heatable material, the sheet or layer having dimensions, volume
distribution, and material properties configured to dissipate power
as heat when operatively coupled to an external oscillating
magnetic field penetrating the base or walls and contacting the
cartridge body; and b) further comprising a latching functionality
for securing the cartridge body within the cavity of the cup or
vessel, wherein the latching functionality is disengageable by the
user for transferring the cartridge from cup to cup or vessel to
vessel. The sheet, plate or layer of inductively heatable material
optionally may also comprise an array of perforations or
dimples.
[0019] In a second embodiment, the invention is a reusably
insertable heating cartridge for inductively heating a food or a
liquid in an inside cavity of a cup or vessel, the cup or vessel
having a base and walls, where the base is composed substantially
of a dielectric material, which comprises: a) a cartridge body for
insertion into the inside cavity of the cup or vessel, the
cartridge body having upper face, peripheral edge and undersurface,
and further comprising a layer, sheet or plate of an inductively
heatable material, the sheet or layer having dimensions, volume
distribution, and material properties configured to dissipate power
as heat when operatively coupled to an external oscillating
magnetic field penetrating the base or walls and contacting the
cartridge body; and b) encapsulated in the cartridge body, i) an
RFID tag and antenna; and ii) optionally a temperature sensor in
electronic communication with the RFID tag and antenna. The sheet,
plate or layer of inductively heatable material optionally may also
comprise an array of perforations or dimples.
[0020] In a third embodiment, the invention is a reusably
insertable heating cartridge for inductively heating a food or a
liquid in an inside cavity of a cup or vessel, the cup or vessel
having a base and walls, the base composed substantially of a
dielectric material, which comprises: a) a cartridge body for
insertion into the inside cavity of the cup or vessel, the
cartridge body having upper face, peripheral edge and undersurface,
b) wherein the cartridge body comprises a sheet or plate of an
inductively heatable material; and wherein the sheet or plate is
further characterized as having an array of perforations or dimples
configured to increase apparent inductive load resistance of the
heating cartridge due to eddy current losses when operatively
coupled to an external oscillating magnetic field penetrating the
base or walls and contacting the cartridge body. Optionally, the
cartridge body may also comprise an RFID tag with antenna and
sensor package. Optionally, the cartridge body also comprises a
mechanical or magnetic latching functionality for detachably
securing the cartridge in the cup or vessel.
[0021] Combinations of the above with vessels or with induction
heating or cooking units are also conceived. These combinations
include combinations of a cartridge and a vessel or a cartridge
configured to operate with an induction heating unit. Such systems
include induction hot plates or other appliances supplied with
compatible electronics and provision for sensor-mediated power
control and safety features.
[0022] In this way, new applications for inductive heating are
found. Vessels lacking an inductively heatable base or baseplate
material may be made responsive for induction heating by inserting
an induction heating cartridge formed as a reusable, immersible
member that can be transferred from cup to cup or vessel to vessel
as desired by the user.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] The teachings of the present invention can be more readily
understood by considering the following detailed description in
conjunction with the accompanying drawings and claims, in
which:
[0024] FIG. 1 is a cross-sectional view through an immersible
cartridge with body, coating and internal layer of an inductively
heatable material.
[0025] FIG. 2 illustrates use of an immersible cartridge with
ferromagnetic layer to heat a liquid in a mug on an inductive
heating unit. Also shown is a retaining magnet for securing the
cartridge in the mug.
[0026] FIG. 3 illustrates use of the magnet to retain a cartridge
with ferromagnetic layer in a mug when tipped so that any fluid
drains out.
[0027] FIG. 4 shows a perspective view of an immersible cartridge
with elastic retaining prongs for insertion into a cup or mug.
[0028] FIG. 5 shows a perspective view of an immersible cartridge
with perforations to increase eddy current density and reduce
weight.
[0029] FIG. 6 is a schematic view of a cup with inserted cartridge
having a inductively heatable layer formed as a perforated collar
and a hob adapted with vertical coils for coupling to the
cartridge. The perforated collar serves mechanically to retain the
cartridge in the cup.
[0030] FIG. 7 is a cross-section of an elastic collar for
reversibly retaining an immersible cartridge in a cup adapted with
center post for receiving the cartridge.
[0031] FIG. 8 is a cross section of a mechanical latch for
reversibly retaining an immersible cartridge in a cup adapted with
center post for receiving the cartridge.
[0032] FIGS. 9A and 9B show an immersible cartridge with extensible
clip for attachment to the wall of a mug or other vessel.
[0033] FIG. 10 is a schematic in cross-section of an immersible
cartridge in a cup. The device is provided with a detachable magnet
placed in an adaptor that is fitted on the outside base of the
cup.
[0034] FIG. 11 is a schematic in cross-section of an immersible
cartridge and cup combination, where the cup is provided with an
embedded magnet for affixing the cartridge.
[0035] FIG. 12 is a schematic showing an immersible cartridge with
external retaining disk, each with a mating magnet.
[0036] FIG. 13 is a schematic of an immersible cartridge with
buoyant floats disposed laterally. The floats compressively affix
the cartridge within the cup, and when not properly seated, the
cartridge floats to the surface of the liquid.
[0037] FIGS. 14A and 14B depict a buoyant cartridge for use in
specialized vessels.
[0038] FIGS. 15A and 15B depict use of the cartridge of FIGS. 14A-B
a baby bottle fitted with a magnetic adaptor for the base of the
bottle.
[0039] FIGS. 16A, 16B and 16C illustrate alternative material
cross-sections.
[0040] FIG. 17 shows a cutaway view of a combination of a cup,
internal cartridge with RFID tag with temperature sensor, and an
inductive heating unit.
[0041] FIG. 18 is a cross-sectional view of an inductive heating
cartridge with RFID tag and temperature sensor. In this embodiment,
no retaining functionality is required.
[0042] FIG. 19 is a view of a combination of a cup, internal
cartridge with RFID tag, and inductive heating unit.
[0043] FIG. 20 is a view of an inductive heating cartridge with
RFID and temperature sensor adapted for use in a bowl or pan where
no retaining functionality is required.
[0044] FIG. 21 is a block circuit diagram of an RFID chip with
antenna assembled in a cartridge for induction heating unit
communication and control.
[0045] FIG. 22 is a plot of temperature versus time for the heating
of 0.75 L of water with an inductive immersible cartridge of the
invention.
DETAILED DESCRIPTION
[0046] Although the following detailed description contains many
specific details for the purposes of illustration, one of skill in
the art will appreciate that many variations, combinations,
substitutions and modifications of the following details are within
the scope of the invention. Accordingly, the exemplary embodiments
of the invention described below are set forth without any loss of
generality to, and without imposing limitations upon, the claimed
invention.
DEFINITIONS
[0047] Certain meanings are defined here as intended by the
inventor, ie. they are intrinsic meanings. Other words and phrases
used here take their meaning as consistent with usage as would be
apparent to one skilled in the relevant arts. When cited works are
incorporated by reference, any meaning or definition of a word in
the reference that conflicts with or narrows the meaning as used
here shall be considered idiosyncratic to said reference and shall
not supersede the meaning of the word as used in the disclosure
herein.
[0048] "Cartridge" or "puck": an insertable layer of an inductively
responsive material formed as a body or member having a shape and
stiffness adapted for handling and for insertion into the inside
cavity of a cup or vessel. The cartridge body is generally a thin,
stiff disk or puck-like form adapted and contoured for close
apposition to the base of a vessel or cup when inserted therein.
When the base of the vessel or cup is placed on the hob of an
induction heating system, the inductively responsive layer of the
cartridge is in proximity to and becomes coupled to the oscillating
external magnetic field generated by the induction heating system.
The cartridge body is optionally provided with a food-safe exterior
coating, and is optionally configured with mechanical or magnetic
functionality for attaching and securing the cartridge inside the
vessel.
[0049] Inductive heating: relates to heating by electrical
induction, where an oscillating magnetic field heats an inductively
responsive material by induction of eddy currents and, in case of
ferromagnetic materials, by magnetic hysteresis.
[0050] Inductively heatable materials: materials in which
significant electrical current is induced when said material is
subjected to a changing magnetic field, currents which, by the
Joule effect, produce heat; ie. materials that are responsive to an
oscillating magnetic field and dissipate the power of the field by
generating caloric heat. These materials include without limitation
iron, cast iron, steel, carbon steel, stainless steel, martensitic
stainless steel, cobalt steel, chrome steel, nickel steel, silicon
steel, magnetic stainless steel, spring steel, mu-metal, their
alloys and their combinations. Aluminum and copper and their alloys
are responsive to magnetic fields but their use is not practicable
with the majority of currently available inductive heating
appliances. In one embodiment, the inductively heatable material
has a Curie temperature selected as a safety feature for the
application.
[0051] Insertable: something inserted or to be inserted, able to be
inserted; able to be put into something else, as in an "insertable
cartridge", where the cartridge is inserted into the interior
cavity of a vessel.
[0052] RFID: ("radio frequency identification") refers to a data
collection technology that uses electronic tags for transmitting
data. The tag, also known as an "electronic label," "transponder"
or "code plate," is made up of an RFID chip attached to an antenna.
Transmitting in the kilohertz, megahertz or gigahertz ranges, RFID
tags may be battery-powered or derive their power from the RF waves
coming from the reader. Like barcodes, RFID tags identify items.
However, RFID tags hold more data than barcodes and unlike
barcodes, which must be in line of sight to the scanner for
reading, RFID tags do not require line of sight and can be embedded
within a body and immersed in a liquid while still functioning.
"Passive" tags have no power source but use the electromagnetic
waves from the "reader" or primary coil to energize the chip and
transmit back (backscatter) their data. Some tags can include a
sensor and A/D converter that, when interrogated, reports the
temperature of a thermal mass in which the tag is embedded, or
other sensory information.
[0053] Hob: as used here, is the flat top part of a cooker, or
"cook-top", containing thereinunder an inductive heating coil or
coils. The induction transfer coil is typically a planar spiral
located immediately underneath and coplanar with the hob but may
also include more complex structures with coils extending out of
plane to more efficiently couple the driving magnetic field with
the load device. Hobs may include portable desktop appliances such
as coffee warmers.
[0054] Induction Heating System, appliance or "unit": includes a
power supply, typically with provisions for rectifying and
filtering an AC voltage, and an inverter for supplying a variable
current to an inductive coil. Generally, the coil is part of a
parallel or series LC tank circuit and is operated at or in the
vicinity of the resonant frequency. Typically, the tank circuit has
little resistive loss except due to heating as a result of magnetic
field coupling with the cartridge body layer, which functions as a
resistive load in parallel with the LC tank. To drive the circuit,
resonant switching is generally achieved either by half-bridge
series resonant converters or by the less expensive quasi-resonant
converters, and is generally zero voltage switching (ZVS) or zero
current switching (ZCS). For example, insulated gate bipolar
transistors (IGBT, U.S. Pat. No. 4,364,073) have made driving these
resonator circuits much more efficient. Inductive systems may
include subsystems for power control and safety features such as
"pot detection". Operation and design of inductive heating systems
are generally known in the art.
[0055] A "vessel" is an article generally for preparation of or for
containing a food or beverage, having a peripheral wall, a lip, a
generally flat bottom with external base, and an internal or inside
cavity, where the inside cavity is generally accessible through an
opening at the top of the vessel. As suitable for use with the
cartridges of the invention, the baseplate, including base and
lowermost aspect of the vessel, is `substantially composed of` or
`essentially composed of` a dielectric material. For example, the
vessel may be made of ceramic, earthenware, stoneware, porcelain,
glass, plastics in general, treated paper, and so forth. As used
here, the inside wall is generally intended to withstand
temperatures up to 290.degree. C. (.about.550.degree. F.), although
not limited thereto.
DESCRIPTION OF THE FIGURES
[0056] Turning now to FIG. 1, illustrated is a cross-sectional view
through an immersible cartridge (1) of the invention with body (11)
formed of a layer, sheet or plate (12) of an inductively heatable
material and optional sanitary coating (13). The inductively
responsive material is chosen so that sufficient electrical
current, known as eddy currents, will flow in closed paths in the
material to produce I.sup.2R dissipation; where the eddy currents
are associated with induced voltages developed in the material by
the application of a changing magnetic field. Unlike an ordinary
vessel, the inductive cartridge can be more specifically tailored
to be inductive heating. The relative thickness, dimensions,
magnetic permittivity, and volume distribution of the material may
generally be chosen to meet certain requirements for eddy current
losses and heat distribution over the body of the cartridge.
[0057] Ferromagnetic materials are preferred due to their magnetic
permeability and relative higher electrical resistance. Suitable
materials include iron, cast iron, steel, carbon steel, stainless
steel, martensitic stainless steel, cobalt steel, chrome steel,
nickel steel, silicon steel, magnetic stainless steel, spring
steel, mu-metal or composites thereof. Aluminum and copper may be
used for induction heating but their requirements are more
demanding than ferromagnetics. They are in general not usable with
current on-the-market induction cooking appliances.
[0058] Useful thicknesses for the present cartridges are generally
in the range of 0.3 mm to about 1.3 mm. Disposable aluminum foils
of 0.003 to 0.05 millimeters (about 0.1 to 2 mils) proposed by
Harnden (see FIG. 6 of U.S. Pat. No. 3,786,222, where results are
shown for a range of 0.1 to 2 mils) do not, by themselves, provide
the stiffness that would be required for reusability and have low
thermal mass and low lateral heat transfer capabilities.
[0059] The performance of a sheet material can be modified by
selective perforation to modify the volume distribution, which
changes the density of the eddy currents according to the volume
distribution per unit surface area. Perforations may be densely
spaced as arrays and hole diameters can be small as required to
achieve coupling. There may also be dimples rather than
full-thickness holes.
[0060] A set of cartridges may be provided in various nested
dimensions so that a cartridge most well fitted to a particular
vessel may be selected. The cartridge does not inelastically
impinge on the walls of the vessel. This approach eliminates the
problem of thermal expansion mismatch between the baseplate of the
vessel and an embedded metallic insert.
[0061] A coating is required if the inductively heatable layer is
not compatible with comestibles. Such coatings as are suitable
include enamel, glazes, such as ceramics, and a dip or
encapsulation in a plastic such as polyimide, silicon, or a
fluoropolymer.
[0062] In operation, the heated induction cartridge (1) lying at
the bottom of a vessel such as a coffee cup (21) will be heated by
an oscillating external magnetic field, and in turn will use
thermal convection to efficiently heat the liquid inside, as shown
in FIG. 2. Cup (21) is shown seated on an inductive heating unit
(23). The induction cartridge in this embodiment is composed of a
ferromagnetic layer and is attached or retained in its place near
the bottom of the cup in close proximity to the primary coils (24)
of the heating unit by use of a retaining magnet (22) installed
under the base of the cup. The inductive cartridge may be removed
from the cup at will and may be inserted in a second cup or
alternate vessel as desired by the user. A grip or handle useful
for this purpose may be added to the cartridge body if desired.
[0063] The advantage of the retaining functionality is demonstrated
in FIG. 3, where the cup (21) containing a liquid (30) is tilted to
pour out or drink the liquid while retaining the cartridge in
place, which happily remains magnetically attached to the inside
bottom of the vessel. The magnet (22) acting as a magnetic "latch"
is affixed under the base of the cup in an adaptor (32) shown here.
If not so restrained, the hot cartridge could tumble out of the cup
while the user is drinking from the cup for example, a circumstance
to be avoided because it might result in burns, spills, and water
damage. In some embodiments, as will be described below, a
"latching functionality" or "attaching device" is not required.
[0064] As an overview, the latching functionality or "retaining
means" for attaching and securing the cartridge in the cup or
vessel may be selected from mechanical "latches" or magnetic
"latches". Embodiments of the mechanical latch functionality
include, without limitation, "spring" or "impingement" latches,
"friction" latches, "clip" latches, barbed latches, threadable
latches, and "pinch" latches, for example. Magnetic latches rely on
magnetic attraction to secure the cartridge in the vessel.
Generally a magnet and a magnetically responsive material are
positioned on opposite sides of the base of the vessel to form the
magnetic latch, but optionally the magnet may be embedded in the
base of the cup.
[0065] The latching functionality is disengageable by the user. The
user, by disengaging the mechanical or magnetic latch, may remove
the cartridge from one cup or vessel and transfer it to another. In
this way each cartridge is versatile in uses, permitting heating
and cooking in any of multiple vessels as desired by the user.
[0066] FIG. 4 shows a perspective view of an immersible cartridge
(40) having elastic retaining prongs (41) or projections (for
insertion into a cup or mug). This illustrates a mechanical
latching functionality. The spring-like prongs (41) arrayed around
the peripheral edge of the central disk (42) of the cartridge are
deformed by insertion in the cup and wedge the cartridge against
the bottom inside surface, ensuring optimal coupling with the power
of the external coil of the heating unit. The cartridge is punched
out at the center (43) to better match the active surface of a
conventional coil. It has been found that such plates are not
heated uniformly, but the heating patterns are more intense along
the eddy current paths which most closely follow the geometry of
the coil. The cartridge may also be contoured across the disk (42)
so as to more closely appose the bottom contour of a conventional
coffee mug. While this feature contributes to a modest improvement
in efficiency, it also increases the stiffness of the center disk
so as to resist bending during frequent handling. It also reduces
weight. Inductive cartridges of this type may be coated with a
sanitary finish or may be used without coating if formed of a
suitable food-safe material. If needed, a coat of fluoropolymer
such as Teflon*), or a ceramic overcoat may also be used.
[0067] FIG. 5 is a perspective view of an immersible cartridge (50)
with perforations to increase eddy current density. Peripherally
disposed prongs (51) are spring-like and are used to secure the
cartridge in a coffee cup or mug, for example. The perforations
(54) in the center disk (52), counterintuitively, have the effect
of improving the induction process and are effective for example in
stainless steel plates having a thickness of about 0.03 inches with
a hole size of about 0.1 inches and an average hole separation of
about 0.15 inches, while not limited thereto. Body disk (52) and
center hole (53) correspond to the shape of a conventional
inductive heating coil.
[0068] FIG. 6 is a schematic view of a cup (61) with an inserted
cartridge (60) having a inductively heatable layer (62) formed with
a perforated collar (63) and a heating unit (65) adapted with
vertically wrapped coils (66) for coupling to the collar (63) of
the cartridge and supplementing the conventional planar spiral
coils of the hob (67) in this embodiment. The spokes (64) of the
perforated collar are diametrically compressible to mechanically
retain the cartridge in the cup. Other vessels may be similarly
adapted.
[0069] FIG. 7 shows a cup (71) containing a cartridge (70) with
central open core fitted with an elastic friction collar (73) for
reversibly retaining the cartridge on a center post (75) adapted
for receiving the collar. The center post is formed as a projection
of the base of the cup. Also shown are perforations (76) in the
disk body (72) for extraction of the disk. A pair of tongs or other
extraction device is used to grip the disk at perforations (76) and
pull it from the cup.
[0070] FIG. 8 shows a cup (81) fitted with an inductive cartridge
(80) having a mechanical latch (82). The cup is adapted with a
center post (83) for receiving the cartridge. The mechanical latch
is mounted on a bezel and is barbed to affix itself to the
centerpost of the cup and can be removed by disengaging the
barbs.
[0071] In related configurations (not shown) the cartridge can be
provided with peripheral externally projecting barbs for fitting
into barb-receiving receptacles, or may be threaded into receiving
channels or mounting pegs on the inside walls of the vessel.
Similarly, a pair of slots extending from top to bottom on the
inside walls of a mug or other straight walled vessel may be
configured to receive a cartridge having mating male pins; the
slots terminate in an "ell" so that a small twist of the cartridge
secures it at the required depth in the mug by the pins. More
generally, a threadable latching feature includes at least two
contralaterally placed pins or slots on the peripheral edge of the
cartridge body, where the pins or slots are configured for engaging
mating threadable channels or bosses in the body of the vessel.
[0072] FIGS. 9A and 9B show a cup (21) fitted with an immersible
cartridge (90) with clip (92) for attachment to the lip (21a) of
the wall of the cup or other vessel. The clip (92) is optionally
extensible to better fit the vessel and ensure that the disk (91)
of the cartridge body is in close apposition to the inside bottom
of the vessel cavity. The clip arm may be formed with a slotted
mounting arm (92b) and extensible arm (92a) with tensioning pin
(93) for adjusting the fit. Alternatively, the clip arm may be a
single piece plastic molded part that is proportioned to generally
fit a standard coffee mug.
[0073] We turn now to magnetic latches for affixing the cartridge
in a vessel. For convenience of illustration, a coffee cup (21) is
used to illustrate various combinations, but the magnetic latches
may be adapted to other dielectric vessels as required. The
magnetic latch is a latching or attachment functionality and is not
used as an inductive heating element. Ceramic magnets deficient in
inductive coupling strength may be used in place of ferromagnets in
the construction of magnetic latches. As before, the attachment of
the cartridge in the vessel is reversible so that the cartridge can
be exchanged between various vessels at the will of the consumer.
The magnetic latch is a combination of a magnetically responsive
element in the body of the cartridge and a magnet applied
externally to the base of the vessel or embedded within the base.
The magnet and magnetically responsive elements are magnetically
attracted, thereby magnetically securing the cartridge within the
vessel.
[0074] FIG. 10 is a schematic of a cup (21) with internal reusable
attachable cartridge (100) shown in cross-section. The device is
provided with a detachable magnet (22) in an adaptor plate (103)
that is fitted on the outside base of the cup.
[0075] FIG. 11 is a schematic of a cup or other vessel (21) and
shaped cartridge (110) in cross-section showing an immersible
cartridge-and-cup combination, where the cup is provided with an
embedded magnet (112) for magnetically attracting and retaining the
ferromagnetic plate or disk forming the body of the cartridge.
[0076] FIG. 12 is a schematic of a cup or other vessel (21) showing
an immersible cartridge (120) with on-board accessory magnet (122).
The on-board accessory magnet is affixed to the disk body (121) of
the cartridge in a molded housing (123). A magnetic latch magnet
(22) affixed to the base of the vessel in an adaptor plate (103) is
used to reversibly capture the cartridge in the bottom of the cup
so that the vessel may be safely inverted without dislodging the
cartridge.
[0077] FIG. 13 is a schematic of a cup (21) fitted with an
immersible cartridge (130) with buoyant floats (133a,133b) disposed
laterally and affixed to the disk body (131) at the peripheral
edges of the cartridge. The buoyant members may be made of
closed-cell foam (134), for example. The buoyant members also
compressively affix the cartridge within the cup (21), and when not
properly seated, buoy the cartridge to the surface of any liquid in
the cup. Use of buoyant cavities in the cartridge is a safety
feature because it alerts the user and prevents heating of the
cartridge when the cartridge is not properly secured in the bottom
of the vessel. The buoyant cavities may be foam, gas bladders,
rigid cavities, or other suitable buoyant members.
[0078] FIGS. 14A and 14B depict a buoyant cartridge (140) for use
in specialized vessels. Shown first is a plan view (FIG. 14A) and a
cross-sectional view (FIG. 14B). In plan view, the device consists
of a central disk (144) of an inductively heatable material and two
hollow wing sections (145a,145b) that serve as floats. Each float
contains a gas-filled or foam-filled cavity (146a,146b). In
operation, a magnetic latch is used to hold the cartridge at the
bottom or lower aspect of a vessel cavity, but when the magnetic
latch is released, the cartridge floats on the surface of the
liquid.
[0079] FIGS. 15A and 15B depict use of the cartridge (140) of FIGS.
14A-B a baby bottle (151). The bottle is fitted with a magnetic
latch assembly (154) with magnet (22) and adaptor plate (155) that
is mounted on the base (153) of the bottle to secure the cartridge
at the bottom of the bottle during the induction heating process.
The bottle with magnetically captive cartridge is first placed on
an induction heating unit for heating. When heating is completed,
the magnetic latch assembly (154) is detached from the bottle
(double arrow) and the cartridge floats to the surface of the warm
liquid. When the baby bottle is inverted, the cartridge floats away
from the nipple (152), allowing the baby to suckle. Alternatively,
if the magnetic latch is not detached, the cartridge will remain
magnetically latched to the base of the bottle and will not impede
flow.
[0080] FIGS. 16A, B and C represent cross-sections of a thin sheet,
plate or layer of an inductively heatable material. As shown, the
volume distribution per unit surface area of the thin layer may be
varied by design to optimize coupling and power dissipation as
heat. In FIG. 16A, a solid section of a layer or plate (161) is
shown, but the aspect ratio is varied by the provision of an array
of dimples (162) on top and bottom. In FIG. 16B, the plate (165) is
perforated (166) at periodic or irregular intervals to increase
eddy current density in the remaining solid areas. In FIG. 16C, the
thickness of the plate (168) is also varied across the
cross-section, optional including as shown here an array of
perforations (169) through the full thickness. Dimples may be
substituted for the full thickness perforations. Or the solid
material layer may be a fibrous or particulate material. Sandwiched
layers may also be used, for example including a heat spreader in
intimate contact with the inductively heatable material. Also of
interest in the fabrication of the inductively heatable sheet or
layer are metallurgical and materials properties such as the size
and separation of microcrystalline or granular domains in the
metal, and the magnetic permittivity.
[0081] While not bound by theory, the volume distribution per unit
surface area is configured to increase heating efficiency and
satisfy "pot detection" circuits of conventional heating units by
increasing the apparent size of the inductive load resistance
sensed by the primary coil. Thus in selected embodiments, the
sheet, plate or layer of inductively heatable material optionally
may comprise an array of perforations or dimples configured to
increase apparent inductive load resistance of the heating
cartridge due to eddy current losses when operatively coupled to an
external oscillating magnetic field penetrating the base or walls
and contacting the cartridge body.
[0082] FIG. 17 shows a perspective cutaway view of a combination of
a cup (21) and insertable cartridge (170) with a "capsule assembly"
(173) mounted centrally on the upper face of the cartridge body. In
this embodiment, the capsule assembly (173) contains an embedded
RFID tag, an antenna, and a temperature sensor. The capsule may
optionally also contain a handshake circuit for compatibility
verification. Also shown in cutaway view is a desktop inductive
heating unit (175) with hob (176), internal coil (177), and LED
display functions (178). Also shown is a representation of an
ON/OFF switch and temperature setpoint switches (179) that are
linked to the microcontroller that controls the AC invertor
powering the primary coil (177). In this embodiment, the cartridge
body is provided with elastic or spring-like peripheral prongs
(172) for mechanically latching the cartridge within the lower
aspect of the cavity of the cup.
[0083] FIG. 18 is a schematic of a simplified cartridge (180) with
disk body (181) and centrally mounted RFID and sensor capsule
assembly (182). The capsule assembly is mounted through the disk
body and an RFID antenna (187) is located within the lower stem
(184) of the capsule, in this embodiment. The RFID chip (186) and a
temperature sensor (182) in electronic communication with the RFID
chip circuitry are embedded in the capsule housing, which also
serves as a handle for inserting and removing the cartridge from a
vessel. Other sensors such as a thermal overload or dry pot sensor
may also be included. A latching functionality is optional. In some
embodiments, the cartridge with RFID assembly is used in vessels
where latching is not needed, for example in a crock pot or in a
cooking bowl or pan not intended for pouring.
[0084] FIG. 19 is a cross-sectional view of a combination of a cup
(21), internal cartridge (190) with capsule-mounted RFID sensor and
antenna (182), and inductive heating element (199) with hob which
supports the cup during heating.
[0085] The capsule assembly (182) mounted centrally in the top face
of the disk body (191) contains an RFID tag or "chip" (186), linked
temperature sensor (185), and antenna (187). The antenna in the
capsule receives and transmits signal from a secondary coil (195)
in the inductive heating unit. The RFID and sensor functions are
powered passively with energy received from the unit. Contained in
the inductive heating unit is an AC power supply with mains, a
rectifier, an AC solid state inverter (198), the primary coil
(194), a microcontroller (197) for controlling the coil, an RFID
"reader" (196) linked to the secondary antenna (195), a user
display and control interface, and accessory safety circuitry and
wiring as are known in the art.
[0086] In addition to the RFID assembly mounted on the top face of
the cartridge body, the cartridge is also modified with a handle
arm (192) for inserting and removing the cartridge from the cup.
The handle includes a mechanism for adjusting the length of the
arm, upper extensible arm (192a), slotted mounting arm (192b), and
tensioning pin (193), and may be clipped over an upper lip (21a) of
the cup wall.
[0087] FIG. 20 is a modified perspective and schematic view of
another embodiment of the inductive heating cartridge (180) of FIG.
18, with pan (202) and hob (209). The inductively heatable layer or
disk (181) is fitted with a central capsule (182) containing an
RFID tag and antenna. The body disk (181) contains perforations
(189) to drive eddy currents at higher resistance. In this
embodiment, no "latching" or "attachment functionality" is
required. The body of the cartridge is depicted as a flat plate
with central capsule assembly affixed to the top face. Applications
in which no attachment functionality is required include general
cooking in pans or bowls where the vessel is not intended to be
tipped during cooking and serving. In this embodiment, the
advantage of rapid transfer of the cartridge or puck from one
cooking vessel to another outweighs the need or a restraining
latch.
[0088] The cartridge is shown as inserting into a pan 202 and
seating on a hob (209) of an inductive heating unit (200). The
heating unit contains a primary coil (204) with power supply and AC
invertor (208), microcontroller (207) and RFID "reader" (206). The
circuit elements are interconnected, for example by mounting on a
printed circuit board and wired as described below. The RFID reader
includes a pick-up antenna (205) mounted under the hob, and may be
used with any pan that does not shield the coupling of RF field
oscillations between the antenna of the heating unit and the
antenna of the capsule assembly (182). The RFID reader may also
transmit, and may be configured to establish two-way communication
with the RFID chip of the cartridge.
[0089] FIG. 21 is a schematic or block circuit diagram of an RFID
controlled heating unit and coupled cartridge with RFID chip
assembly (210), where the RFID chip and any associated sensors are
contained in the cartridge, cartridge body, or attached thereto. In
operation, the induction heating unit operates from AC power,
converting that to DC via a rectifier bridge circuit (218), which
feeds an AC invertor (217) that powers the primary induction coil
(213). Provision is also made for DC power for the digital
supporting circuitry including microcontroller 215. Microcontroller
215 receives information from the RFID reader 214 and user
interface 216 and is programmed to control the AC inverter output
accordingly. Provision is made for ROM and RAM capacity, data and
address buses, and so forth as is known in the art. The user
interface may include display functions, including temperature
display and system alerts, and controls for adjusting the
temperature and setting a timer, for example. The functionality of
the heating unit may be complex, and optionally includes pot
detection and thermal overload protection.
[0090] The RFID tag in the cartridge is generally powered passively
by capturing RF energy from the primary or secondary coils.
Optionally the RFID control circuit can include a "handshake"
read-write functionality and other "watchdog" circuitry for
ensuring that the cartridge and heating unit will work properly
together (component ID verification). The RFID tag in the cartridge
need not be a simple transponder, and may contain sensor functions
for monitoring temperature in the food or beverage, and includes an
A/D converter for conveying sensor information. A "dry pot"
algorithm can be programmed to guard against the situation when the
cartridge is heated with no liquid in the vessel by determining the
rate at which the temperature reading on the RFID capsule rises
once the unit is powered on. Since the capsule is thermally
insulated from the heatable disk body of the cartridge, the
temperature variation would be minimal. Thus, if the temperature
increase is below a certain limit, say less 3.degree. F. over 20
seconds taking into account heating initiation lag (see FIG. 22),
the unit will turn off Alternatively, a second temperature sensor
can read the temperature on the cartridge body and can be used to
flag early signs of thermal overload. Load coupling can also be
monitored by sensing power dissipation in the inverter LC tank
circuit or by monitoring harmonics of the driving frequency as is
known in the art.
[0091] To establish a handshake, the inductive heating unit or
system will read the RFID tag signal coming from the cartridge and
compare it with a value in memory to identify the cartridge ID and
operating parameters. Power settings may be adjusted based on the
ID of the cartridge. Different cartridges may have different codes
depending on their intended use. Settings preferred by the user,
for example, settings for tea versus coffee, can be stored on board
the heating unit. Conversely, as an added safety measure requiring
two-way communication between the cartridge and the heating unit,
the cartridge can receive a code and compare it with its own
database to determine compatibility, sending a flag to the
microcontroller if a match is not found.
[0092] There are multiple ways the RFID communication between the
cartridge and the induction heating unit can be devised. In circuit
specific for this application, for example, a chip such as the
Maxim MAX6576 (MAXIM, Phoenix Ariz.), if pulse modulation is
desired, can drive the load transistor in parallel with the coffee
cup's RFID coil. The serial data of the temperature sensor will
modulate the load of the coil, which can then be detected in the
baseplate RFID sender/sense coil as voltage envelope changes. For
this method a transmit oscillator is not required. It can send both
serial number and temperature data.
[0093] Another RFID solution which is a preferred embodiment in
this application is to have a standard RFID tag/reader
configuration. A single semiconductor chip like Gentag GT301
(Gentag, Washington D.C.) can perform both identification and
temperature readings. It normally only operates up to 60.degree.
C., but can be operated up to 100.degree. C. with reduced accuracy.
A second generation of the chip should easily work to 100.degree.
C. with a +/-0.5.degree. C. accuracy. The RFID tag can communicate
with a standard RFID reader.
[0094] Cartridges having an embedded RFID tag may be provided with
a mating cup or vessel, the cup or vessel being composed
substantially of a dielectric material and having walls, lip and a
base, wherein the cup or vessel is configured for removably
receiving the insertable heating cartridge.
[0095] Formerly, vessels made of dielectric materials like ceramic,
glass, plastic or paper could not be used for conventional cooktop
cooking. The present invention enables the use of this class of
cookware with conventional induction cooking systems for the
kitchen and desktop systems for the office or home. An inventive
departure from the prior art is as follows. Conventional induction
systems use pot detection subcircuits to power down in the absence
of a pot, a safety feature that prevents heating of small metallic
objects. This feature is incorporated in the electronics of the
unit. The circuits are designed to detect a ferromagnetic pot of
certain size before activation. Thus a combination of a ceramic or
glass vessel and an insertable induction heating cartridge on a
heating system of the prior art is limited to vessels permitting
close proximity of the cartridge to the primary coil. For vessels
with a raised bottom surface, the coupling between the induction
coil and the inductive cartridge may be insufficient and result in
power down. As my experience has shown, even though the magnetic
field would be strong enough to heat the cartridge inside the
vessel, the system would not work. For new induction heating units
with RF capabilities, a RFID tag in communication with the heating
unit will by-pass the pot detector and permit heating. This way,
even a single cup of water, which otherwise would be a load too
small, can be heated and brought to a boil right on the range top
by inserting a small cartridge with RFID into a dielectric cup or
vessel, thereby eliminating the need for old-fashioned and
inefficient electric kettles, ranges, and warmers and expanding the
range of inductive cooking to more generally available kitchenware,
even china.
[0096] Embodiments of the inventive cartridge may also include
configurations having one or more safety features. These include,
encapsulated in the cartridge body or affixed thereto, i) an RFID
tag and antenna configured to respond to a communication protocol
for verifying compatibility of said cartridge and an inductive
heating unit; ii) encapsulated in said cartridge body, an RFID tag
chip and antenna, said cartridge body further comprising a
temperature sensor circuit in communication with said RFID tag chip
for transmitting a temperature datum to a microcontroller of an
inductive heating unit; iii) one or more buoyant cavities, wherein
the buoyant cavity is configured for buoying said cartridge in a
liquid when said cartridge is not latchedly secured in the cavity
of said cup or vessel; or, iv) a layer of inductively heatable
material having a Curie temperature less than 600.degree. F., more
preferably less than 500.degree. F., and most preferredly about
300.degree. F., where the material is used to form the inductively
heatable material, thus reducing the possibility of
overheating.
[0097] In another embodiment the invention is a cartridge
configured to heat a food or beverage in a non-conductive vessel in
spite of the limitations imposed by pot detection circuits of
modern induction heating units. While pot detection circuits are a
safety feature for ensuring that objects such as spoons, lids, and
wristwatches, for example are not heated, and for ensuring that a
pot is always on the hob when the unit is active, the cartridges of
the present invention more efficiently generate heat by being
placed inside the vessel. Thus it may be appropriate to defeat the
pot detection safety circuit on many induction heating units. As is
shown below, surprisingly this can be done while increasing heating
efficiency using cartridges of the present invention where the
cartridge body comprises a perforated plate.
[0098] All the above embodiments the invention are also a method
for promoting the use of induction heating appliances with vessels
not conventionally used with induction heating appliances, such as
those made of china, glass or plastic. The method includes the
steps of supplying an inductive heating cartridge of the present
invention to a consumer, and supplying instructions the consumer to
insert it into a suitable vessel chosen by the consumer and use the
combination with an inductive heating appliance.
EXAMPLES
Example 1
[0099] To form an insertable heating cartridge of the invention, a
puck-shaped piece of stainless steel (T304) was cut from stock as
supplied by the manufacturer. The stainless steel was 0.03 inches
thick and perforated in a regular array with 0.095 inch diameter
holes at 0.16 inch intervals, and had a surface area of about 36
square inches. Other cartridges having other material properties,
thicknesses, and volume distributions were prepared in a similar
way.
Example 2
[0100] FIG. 22 is a plot of temperature versus time for the heating
of 0.75 L of water with an inductive immersible cartridge of the
invention. A non-ferrous pot was filled with water and a cartridge
of the invention was inserted into the inside cavity of the vessel,
which was then placed on the hob surface of an induction heating
unit (Sunpentown Model SR-1881 Induction Cooktop, City of Industry
CA). For the test, the cartridge was immersed inside the vessel in
close apposition or proximity to the inside bottom surface of the
vessel. The induction heating unit was then activated. The graph of
temperature versus time shows a brief lag followed by relatively
linear heating kinetics at medium power.
Example 3
[0101] The Sunpentown Model SR-1881 Induction Cooker, which is
representative of commercially available induction heating units,
is equipped with pot detection circuitry designed to automatically
"power down" if no pot is placed on the surface of the heating unit
or the pot is removed during heating. For the unit to work, the pot
must be ferromagnetic and must have a minimum size.
[0102] It was found by trial and error that raising or lowering a
metal surface near the surface of the cooktop serves as an index of
the success of magnetic coupling required to engage power on the
unit. This index is herein termed the "coupling height index".
Regular steel flat cartridges result in heating if placed in close
proximity to the surface but not when raised higher. When a sheet
of 1018 carbon steel 5.times.5 inches in diameter and having a
thickness of 1 mm was placed on the cooktop in a vessel, the
maximal height achieved before automatic power down is 4.4 mm, a
less than fully satisfactory result based on the needs of the
market. The base of the inside cavity of many ceramic, plastic, or
glass vessels is 8 mm or higher relative to the level of the cook
top surface. Sheets of wire gauze were also unsatisfactory,
resulting in no heating at any height. As a benchmark, the coupling
height index of 4.4 mm achieved with a flat sheet of 1018 steel 1
mm thick was taken as a baseline for further experiments.
[0103] Various materials and thicknesses were then tested.
Unexpectedly, a sheet of T304 martensitic stainless steel, 0.5 mm
thick, having a regular array or pattern of perforations 0.095
inches in diameter and spaced 0.16 inches was found to permit
heating at a higher elevation from the cooktop, achieving coupling
at up to 8.0 mm from the surface--as would be more fully
satisfactory for commercial applications. This is a better than
expected result with almost double the coupling height index
gain.
[0104] The perforation patterns that showed the best results to
date were an array of 0.095 inch diameter holes at 0.16 inch
intervals, which resulted in a coupling height index of 8.0 mm.
Based on multiple experiments with various materials and
configurations, the increase in coupling height index due to
material selection and the increase due to the array of
perforations were separated out. It was estimated that the increase
in coupling height index due to the array of perforations is about
1.5 mm. The increase in coupling height index due to the material
selection, dimensions and the plate thickness is about 2.1 mm. This
shows that 40% of the increase in functional elevation was achieved
due to the use of a sheet with an array of perforations. An array
of dimples may also be used.
[0105] Since the magnetic field decreases exponentially with the
distance, the increase above baseline becomes very significant. Due
to a weakening intensity of the magnetic field as the distance from
the surface of the cooktop increases, the size of the inductive
load perceived by the cooktop circuitry is expected to be reduced.
Surprisingly, the magnetic load of a perforated plate was found to
be perceived by the cooktop as greater than a solid plate. It has
been found that given a choice of material, thickness, and, more
surprisingly, a spaced perforation array will significantly
increase the inductive signature of the induction cartridge so that
the pot detection circuitry reads a normal load and powers up even
though the cartridge is placed at a higher elevation.
[0106] Cartridges cut from other sheet stock, wire mesh, and
non-perforated sheet stock were not successful in coupling with the
heating unit, the perforated sheet material was successfully
coupled to the output of the primary coil and heating resulted. The
pot detection circuit was compatible for heating a perforated
stainless steel sheet immersed in a dielectric vessel, but was not
compatible with a solid isotropic stainless steel sheet of similar
thickness, and was not compatible with very thin foils or wire
gauze.
[0107] After many experiments, cartridges formed from perforated
stainless steel sheet were found to be more compatible with a
conventional induction heating unit than cartridges formed from
very thin or solid sheet.
INDUSTRIAL APPLICABILITY
[0108] The invention lends itself to commercial application through
the provision and sale of the inventive cartridges for insertion
into cups or vessel, where the vessel is provided by the consumer,
so that a food or liquid may be heated with a compatible induction
heating system without need for a special vessel. The cartridges
are immersible and may be removed for washing; such cartridges may
be moved from vessel to vessel at will, or may be adapted with
attaching functionality so that they may be affixed in a particular
vessel. The inventive cartridges may also be sold as a combination
with a cup or vessel adapted for their use as a combination, or may
be sold as a part of an induction heating system having hob, coil,
and compatible electronics, and so forth, while not limited
thereto. Although the foregoing invention has been described in
some detail by way of illustration and example for purposes of
clarity of understanding, it will be clear to one skilled in the
art that changes, substitutions, combinations and modifications may
be practiced within the scope of the appended claims. Therefore,
the scope of the present invention shall be determined not with
reference to the above description but shall, instead, be
determined by the construction of the appended claims, along with
their full scope of equivalents. In general, in the following
claims, the terms used should not be construed to limit the claims
to one or more specific embodiments disclosed in the specification
and the claims, but should be construed to include all possible
embodiments along with the full scope of equivalents to which such
claims are entitled. Reference throughout this specification to
"one embodiment" or "an embodiment" means that a particular
feature, structure or characteristic described in connection with
the embodiment is included in at least one embodiment of the
present invention. Thus, the appearances of the phrases "in one
embodiment" or "in an embodiment" in various places throughout this
specification are not necessarily all referring to the same
embodiment.
[0109] The appended claims are not to be interpreted as including
means-plus-function limitations per 35 USC 112 paragraph 6, unless
such a limitation is explicitly recited in a given claim by using
the phrase "means for." And unless the context requires otherwise,
throughout the specification and claims which follow, the word
"comprise" and variations thereof, such as, "comprises" and
"comprising" are to be construed in an open, inclusive sense, that
is, as "including, but not limited to".
[0110] All of the U.S. patents, U.S. patent application
publications, U.S. patent applications, foreign patents, foreign
patent applications and non-patent publications referred to in this
specification and/or listed in an Information Data Sheet, are
incorporated herein by reference in their entirety.
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